1. Field of the Invention
This invention relates to a movable magnetic head assembly employed in double sided flexible magnetic disk storage devices, and in particular to a construction thereof which enables the flexible magnetic disk (hereafter called a floppy) and the magnetic heads to contact each other only under the force of gimbal springs.
2. Description of the Prior Art
In floppy disk memory devices, as widely used with home computers and word processors, it is necessary to bring the magnetic read/write heads into contact with a thin magnetic coating on the circular Mylar disk at a predetermined pressure to avoid damage to the disk or heads.
FIGS. 1 and 2 show a conventional movable magnetic head assembly for floppy disk memories, wherein a floppy 1 comprises a thin disk 2 coated on both sides with a magnetic storage material 2a and enclosed in a jacket 3 having a head window opening 4 on both sides. Gimbal springs 6a and 6b centrally support magnetic heads 5a and 5b, respectively, and urge them against the disk 2 with an appropriate pressure. A loading arm 7 has a precision injection molded flexure spring 8 inserted in the one end thereof, and has a hollow pedestal surface for attaching the gimbal spring 6a at the other end. A carriage 9 is guided by a pair of parallel rods 10 for radial movement relative to the disk, and defines a pedestal 11 for mounting the spring 8. The heads 5a, 5b are connected to read/write signal cables 12a, 12b, respectively.
The mechanism by which the arm 7 is separated from the disk comprises a cross-arm 13 rigidly fixed to or formed integrally with the arm, and arranged to be physically engaged by hand or by any suitable mechanical or electromechanical arrangement capable of withdrawing the arm against the pressure of the spring 8 in a direction opposite that of arrow A.
A coil spring 14 is disposed between the arm 7 and a support arm 15 secured to the pedestal 11 over the spring 8 by screws 16 for urging the arm 7 toward the disk perpendicularly; this applies a predetermined "pinch" pressure between the disk 2 and the heads 5a, 5b.
In operation, the cross-arm 13 is first moved in the direction opposite arrow A to form an insertion gap for the jacket 3, which has a thickness of "h". After inserting the floppy 1 into the gap, the loading arm 7 is released and moves in the direction of arrow A to bring the heads 5a, 5b into contact to the magnetic material 2a of the disk.
In such a conventional head assembly, there are essentially four spring forces which affect the overall contact pressure between the disk and the heads; the force of the compressed coil spring 14, the force of the flexure spring 8, the inherent spring force of the head cable 12a, and finally the force of the gimbal springs 6a, 6b which support the magnetic heads. Differences in the head contact pressure thus arise due to gravitational forces exerted on the loading arm 7, etc. depending on the orientation of the floppy disk drive mechanism, i.e. horizontally as shown, horizontal but upside down, or vertical. Such contact pressure variations are typically compensated by adjusting the compression strength of the coil spring 14 via means not shown, which is obviously time consuming and troublesome.
Further, since the head cable 12a extends somewhat loosely between the movable arm 7 and the fixed carriage 9, the inherent elastic or spring force attributable to the cable varies widely and with use, which tends to disrupt any fine force adjustments made to the coil spring 14.
These unavoidable contact pressure variations attendant with the conventional magnetic head assembly result in damage to the disk and in unstable signal transducing characteristics.